A drug product (e.g., that contains a protein) can be stored in liquid or lyophilized, i.e., freeze-dried, form. A lyophilized drug product is often reconstituted by adding a suitable administration diluent just prior to patient use.
Active protein may be lost as a result of physical instabilities, including denaturation and aggregation, as well as chemical instabilities, including, for example, hydrolysis, deamidation, and oxidation. The stability of a protein drug in a particular form, e.g., in a liquid or in a lyophilized form, can be an important consideration in selection of a product form.